[lm-sensors] [RFC v2] Support of chassis intrusion detection

[Jean Delvare <khali@linux-fr.org>]

Hi all,

A number of users have asked us to support the chassis intrusion
detection feature which some hardware monitoring chip have. I've
created a ticket for this:
http://www.lm-sensors.org/ticket/2370

I have made a first proposal 3 weeks ago, and got a number of
interesting comments about it. Here comes a second version hopefully
addressing all the concerns that had been raised. Changes include:
* Handle multiple intrusion detection switches.
* Let the user control whether chassis intrusion should result in
  system beeping or not. At least the Winbond W83793G supports this, and
  probably other chips as well.


sysfs interface
=======
intrusion[0-*]_alarm
		Chassis intrusion detection
		0: OK
		1: intrusion detected
		RW
		Contrary to regular alarm flags which clear themselves
		automatically when read, this one sticks until cleared by
		the user. This is done by writing 0 to the file. Writing
		other values is unsupported.

intrusion[0-*]_beep
		Chassis intrusion beep
		0: disable
		1: enable
		RW

drivers
===
Drivers adm9240, w83792d and w83793 implement this feature in
non-standard ways. They should be converted to the new, standard
interface.

libsensors
=====

SENSORS_FEATURE_INTRUSION = 0x19
SENSORS_SUBFEATURE_INTRUSION_ALARM = (SENSORS_FEATURE_INTRUSION << 8) | 0x80
SENSORS_SUBFEATURE_INTRUSION_BEEP = SENSORS_SUBFEATURE_INTRUSION_ALARM + 1 

sensors
===
Reading the value of the chassis intrusion alarm and beep subfeatures
is done like for any other subfeature. Likewise for writing to the beep
subfeature.

Writing to the alarm subfeature, OTOH, can't be handled the same as
writing limits, because we certainly don't want to clear the flag
automatically at lm_sensors start or restart time. So we could add a
dedicated flag to clear the intrusion detection flag (e.g. "sensors
--clear-intrusion").


If anyone has objections or comments, please speak up.

-- 
Jean Delvare

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